Increasingly, white light emitting LEDs (“white LEDs”) are being used to replace conventional fluorescent, compact fluorescent and incandescent light sources in virtually all applications. White LEDs generally include one or more photoluminescence materials (e.g., one or more phosphor materials), which absorb a portion of the radiation emitted by the LED and re-emit light of a different color (wavelength). Typically, the LED generates blue light and the phosphor(s) absorbs a percentage of the blue light and re-emits yellow, green, or a combination of green and yellow light. The portion of the blue light generated by the LED that is not absorbed by the phosphor material combined with the light emitted by the phosphor provides light which appears to the eye as being white in color.
Commonly, white LEDs comprise one or more blue LED chips mounted within a cavity of a package which is then filled with an encapsulant containing the one or more phosphor materials. A disadvantage of such white LEDs is the relatively high cost of the package. Recently, attention has focused on producing white LEDs that avoid expensive packaging by applying phosphor directly to unpackaged LED chips, so called Chip Scale Packaging (CSP) solutions. The present invention concern apparatus and methods of applying coating of photoluminescence materials directly to LED chips.